CCPCHcommon control physical channelCCTrCHcoded composite transport channelISCPinterference signal code powerMACmedium access controlNRTnon-real timeRSCPreceived signal control powerRTreal timeSIRsignal to interference ratioTDDtime-division duplexTFCtransport format combinationTXtransmissionUEuser equipmentUMTSuniversal mobile telecommunications system
For UMTS-TDD systems, in an uplink time slot where the UE has only one CCTrCH, the UE TX power is the TX power of the CCTrCH, which is determined by the TFC used for this CCTrCH. As specified in the standards, when the UE estimates that a certain TFC would require more power than the maximum transmitter power, it should limit the usage of that TFC. The UE continuously evaluates which TFCs can be used for the purpose of TFC selection. The evaluation is performed using the estimated UE transmit power of a given TFC. MAC-d will notify the codec to reduce the data rate, if applicable, by sharing the information as to which TFCs can be used. This is called dynamic link adaptation (DLA).
However, in an uplink time slot where the UE has two CCTrCHs, the UE TX power is the sum of the TX power of the two CCTrCHs. That is, UE TX power is determined jointly by the TFCs of the two CCTrCHs. The current standardized dynamic link adaptation (DLA) algorithm cannot deal with this case, i.e., the UE does not know which TFCs to use or block.
It is desirable to provide a method of enabling a UE to make a decision regarding TFC selection by using dynamic link adaptation (DLA).